I was coding in Scala and I came across this issue. The following code compiles just fine:

val speed: (Int, Int) => Float = _.toFloat / _

and by the same logic I thought this would too, but it does not

val printSpace: String => Unit = print(_ + " ")

Could anyone explain me why?

I tried to change it to

val printSpace: String => Unit = s => print(s +" ")

which works but I do not understand why the first version does not since it specifies that _ is a string